1. The Field of the Invention
The present invention relates to methods and compositions for fire-resistant resin materials that can be used in architectural design applications.
2. Background and Relevant Art
Recent architectural designs have focused on synthetic, polymeric resins, which can be used as windows, partitions, walls, etc., in offices and homes. In particular, decorative polymeric resin materials (or “resins”) are now particularly popular compared with decorative cast or laminated glass materials since decorative resins can be manufactured to be more resilient, and to have the same transparent, translucent, or colored appearance as cast or laminated glass, but with less cost. Decorative resins further provide more flexibility, compared with glass, in terms of color, degree of texture, gauge, and impact resistance. Furthermore, decorative resins have a fairly wide utility since they can be formed to include a wide variety of artistic colors and images. This flexibility applies both in the manufacturing phase, as well as in the post-manufacturing, or ultimate-use, phase.
Present polymeric resin materials generally used for creating decorative resin panels comprise polyvinyl chloride or “PVC”; polyacrylate materials such as acrylic, and poly(methylmethacrylate) or “PMMA”; polyester materials such as poly(ethylene-co-cyclohexane 1,4-dimethanol terephthalate), or “PET”; poly(ethylene-co-cyclohexane 1,4-dimethanol terephthalate glycol) or “PETG”; glycol modified polycyclohexylenedimethylene terephthalate, or “PCTG”; as well as polycarbonate materials. While each of the aforementioned resin materials can serve as an appropriate glass substitute, each resin material varies in physical properties from one material to the next. For example, polycarbonates, and polyesters (e.g., PETG, PCTG, and PET, also referred to as “copolyesters”) are generally used in solid, extruded sheet form. An extruded resin sheet is generally a solid preformed sheet, such as a solid 4′×8′ resin sheet (alternatively, 3′×5′ sheet, 6′×10′ sheet, etc.), which ultimately can form a surface of a decorative resin panel in final form.
One advantage of extruded materials, such as extruded polycarbonate, extruded PCTG, or extruded PETG, is that extruded resin sheets can be manipulated in one or more ways for a variety of design effects. For example, a colored or textured decorative panel, that is suitable for use as a building material, can be created by combining one or more transparent or translucent extruded resin sheets with one or more colored or textured fabrics. Alternatively, a decorative panel that is also suitable for use as a building material can be created by embedding certain three-dimensional objects between two or more transparent or translucent extruded resin sheets. Generally, these sorts of design modifications do not inhibit the strength of the decorative panel as a building material. As such, extruded resin materials can be both visually appealing, and structurally useful. Unfortunately, there is a reluctance to use resin materials in some cases due to fire safety concerns.
In some cases, synthetic resin materials can be made to have some fire-resistive properties by adding a flame-retardant to the resin material prior to extrusion. Generally, flame-retardant additives (or “flame-retardants”) can be categorized by three basic mechanisms. For example, vapor phase flame-retardants work in the vapor phase by free radical flame poisoning, which removes active free radicals that promote further exothermic reactions. Example vapor-phase flame-retardants include halogenated materials (with or without the addition of antimony synergists). Solid-phase flame-retardants promote the formation of char in the solid phase to form an insulating layer. The insulating layer protects the flammable substrate from the fire, and reduces the emission of volatile flammable gases into the fire. Example solid-phase flame-retardants include phosphorus and silicone compounds. Heat sink flame-retardants work in endothermic reactions by releasing water and/or carbon dioxide, which quench the fire.
Some examples of making resin materials flame-retardant with certain additives include U.S. Pat. Nos. 5,258,432 and 5,204,394, which disclose combining phosphorous-based compounds (solid-phase) with resin materials such as polycarbonate mixtures. U.S. Pat. No. 5,109,044 discloses combining flame-retardants, such as haloaryl phosphates, with resin materials such as carbonate polymer blends. U.S. Pat. No. 5,663,260 discloses the use of low levels (less than about 1%) of phosphorus compounds with an alkali metal salt to achieve UL-94 (V2) in resin materials, such as polycarbonate resins. Unfortunately, as is understood from the foregoing and other examples, adding flame-retardant compounds to a resin material typically involves adding some fire-resistive properties to the resin material at the expense of other important architectural design properties, such as strength or translucence.
For example, a resin material can be made at least somewhat fire-resistant by adding a relatively large amount (ranging from about 5% to about 60%) of flame-retardant prior to extruding the resin material (i.e., forming an extruded resin sheet). A large amount of flame-retardant, however, can also have the effect of lowering—rather than raising—the melting point of the resin material. For PCTG or PETG, a preferred architectural design material, this has structural and design consequences that limit extruded PCTG or PETG panels to indoor use, or to outdoor use only in relatively cool climates. Furthermore, as previously described, a lower melting point can increase the fire risk associated with the resin material. In addition, a large majority of solid flame-retardants are opaque, such that most fire resistant panels are not sufficiently clear or translucent for architectural purposes. By contrast, those resin materials that are sufficiently useful for architectural applications, do not have enough fire-resistance properties to qualify the resin materials as suitable for “Class A” building environment.
In particular, most conventional architectural resin materials will melt or soften, such that they are unable to maintain minimum structural rigidity at the conditions identified by Class A standards. This poses a risk for not only architectural resin materials that would otherwise be used outdoors in a hot climate, but also, in the event of a fire, for resin materials used inside a building. Furthermore, the melted portions of such resin materials are sometimes more flammable than when solid, such that the resin materials can actually pose a greater fire and smoke hazard.
In general, “Class A” standards have the pertinent minimum requirements of a smoke density value of less than 450%-light absorption/minute, and a flame spread value of less than 25 ft/minute, over not less than a 10 minute span at a certain heat. Examples of this include the current versions (as of 2005) of the Underwriters Laboratories, Inc. 723 standard (“UL-723”), or the American Society for Testing and Materials E-84 standard (“ASTM-E84”), and so forth. Other related standards include the current (as of 2005) versions of the American National Standards Institute/National Fire Protection Association No. 255 (“ANSI/NFPA No. 255”), and Uniform Building Code No. 8 (“UBC No. 8”). (The foregoing standards or materials satisfying or articulating the minimum smoke and flame spread values stated above are hereinafter referred to generally as “Class A”, “Class A standards” or “Class A materials”.)
There are some resin materials that satisfy certain fire-rating standards under certain, modified conditions. Unfortunately, these fire-resistive resin materials usually have a number of limitations that make them undesirable for use in architectural and general building material contexts. For example, relatively thin decorative resin panels (e.g., 1/16th of an inch thick or less) may be sufficiently translucent and fire-resistant in some cases, but do not have enough structural rigidity to have meaningful semi-structural and/or decorative architectural application. Furthermore, some resin manufactures have used an adjusted standard (e.g., a 3 minute smoke test, rather than the conventional 10 minute smoke test) to claim fire-resistance properties in a translucent resin.
While this might provide the manufacturer with some claim to fire resistance, the application context for materials passing only under a modified standard is nevertheless quite limited. Alternatively, the resin materials are not transparent or translucent—or cannot be easily made transparent or translucent—such that the resin materials cannot easily be colored, or modified to embed certain objects. It should be noted, in any event, that conventional resin materials typically do not pass the unmodified ASTM E-84 standard. As such, conventional resin materials, and even resin materials having claims to fire-resistance are generally unsuitable for architectural design purposes under actual, unmodified Class A fire safety guidelines.
Accordingly, an advantage in the art can be realized with architectural resin materials that meet relatively high fire standards, and maintain important aesthetic and structural properties, such as an appropriate degree of translucence, as well as strength. In particular, an advantage can be realized with visually appealing, translucent resin materials that qualify as a Class A fire resistant materials under conventional, unmodified testing guidelines.